Hot gas generators



Nov. 24, 1970 E. KELLETT 3,541,790

now GAS umnnm'rons Filed Oct. 5, 1968 2 Sheets-Shed 1 I I I I l I I I I I I I I I ATTORNEYS Nov. 24, '1970 a. KELLETT 3,541,790

now GAS umnxrons Filed Oct. 5, 1968 1 2 Sheets-Sheet 8 NTOR MW ATTORNEYS 3,541,790 HOT GAS GENERATORS Eric Kellett, Ealing, London, England, assignor to C.A.V. Limited Filed Oct. 3, 1968, Ser. No. 764,840 Claims priority, application Great Britain, Oct. 5, 1967, 45,458/ 67 Int. Cl. F02c 7/08 US. Cl. 60-3952 1 Claim ABSTRACT OF THE DISCLOSURE This invention relates to hot gas generators of the kind comprising in combination, a combustion chamber, a turbine which is driven by exhaust gases leaving the combustion chamber, a first compressor driven by said turbine for providing dilution air to the combustion chamber, and a second compressor for providing an air/fuel mixture to a burner disposed within the combustion chamber.

With such generators the exhaust gases leaving the turbine contain undesirable combustion products if the combustion temperature exceeds a certain value, and the object of this invention is to provide such an apparatus in a form in which the possibility of the generation of undesirable combustion products is minimised.

According to the invention in a generator of the kind specified, a portion of the exhaust gases leaving the turbine is admitted to the inlet of the second compressor thereby reducing the combustion temperature.

In the accompanying drawings:

FIG. 1 is a sectional side elevation of one example of a hot gas generator to which the invention may be applied and FIG. 2 is a diagrammatic representation of the generator of FIG. 1 modified in accordance with the invention.

Referring to the drawings there is provided a body part 10 in which is mounted a rotary shaft 11. At one end of the shaft is mounted a radial flow turbine rotor 12 which is accommodated within a turbine casing 13 having a tangential inlet 14 and an axially extending outlet 15. The turbine casing is secured to the body part 10. At the other end of the shaft is mounted a pair of radial flow compressor rotors 16 and 17 disposed in compressor casings 18 and 19 respectively. The compressor defined by the rotor 16 and casing is hereinafter called the first compressor whilst the compressor defined by the rotor 17 and the casing 19 is hereinafter called the second compressor. The casings 18 and 19 have tangential outlets 20 and 21 respectively and inlets 22 and 23.

Also provided is a combustion chamber indicated at 24 and this includes an outer casing 25 which is of generally cylindrical form and having a throat portion 26. The downstream end of the combustion chamber is secured ted States Patent 0 to the inlet 14 of the turbine and upstream of the throat portion is an annular carrier 27 which serves to support the downstream end of a flame tube 28. The upstream end of the flame tube is supported by a burner assembly 29 secured to the upstream end of the outer casing. Surrounding the flame tube is an annular space to which dilution air is fed by the second compressor through a pipe 29. Formed in the flame tube are holes 30 through which the dilution air flows into the flame tube. Furthermore, the burner assembly 29 is in communication with the outlet 20 of the first compressor by way of a pipe 31.

Also mounted on the casing 25 is an ignition plug 32 which extends into the flame tube downstream of the burner assembly 29 so as to ignite the air/fuel mixture entering the combustion chamber.

In order to entrain fuel with the air entering the first compressor a carburettor indicated at 33 in FIG. 2 is provided. The carburettor is supplied with fuel from a source 34 and when liquid fuel is employed a conventional fuel carburettor having a venturi may be provided in order to draw the fuel into the air stream. Where a gaseous fuel is used such for instance as town gas, natural gas or vapourised petroleum gas, the gas will be supplied under a slight pressure to the nozzle of the carburettor so that the latter is little more than a mixing device for the air and gas.

In operation the heated gases leaving the combustion chamber drive the turbine rotor prior to being discharged through ducting or the like. The turbine rotor in turn drives the compressor rotors which supply the air/fuel mixture and the dilution air to the combustion chamber. The dilution air acts to reduce the temperature of the gases entering the turbine so that the safe working temperature thereof is not exceeded.

With such an arrangement it has been found that the exhaust gases leaving the outlet 15 of the turbine can contain undesirable combustion products. This depends upon the type of fuel used but also upon the combustion temperature. It has been found that if the combustion temperature is increased then the degree of contamination also increases.

In order to limit the combustion temperature a portion of the exhaust gases leaving the outlet of the turbine are admitted to the inlet 22 of the second compressor. The exhaust gases leaving the turbine have a lower oxygen content than pure air and therefore the combustion temperature will be lowered. As shown in FIG. 2 the exhaust gases are conveyed along a duct 35 to a point downstream of the carburettor 33 and for controlling the quantity of gas flowing a valve 36 is provided. In this manner the combustion temperature can be controlled.

Having thus described my invention what I claim as new and desire to secure'by Letters Patent is:

1. A hot gas generator comprising in combination, a combustion chamber, a burner disposed in the combustion chamber, a turbine which is driven by exhaust gases leaving the combustion chamber, a first compressor driven by said turbine for providing dilution air to the combustion chamber to control the temperature of the exhaust gases entering the turbine, a second compressor driven by the turbine for delivering an air/fuel mixture to the burner, a duct through which the exhaust gases can flow between the outlet of the turbine and the inlet of the second compressor and valve means for controlling the flow of gas through said duct, the exhaust gas when mixed with the air/fuel mixture supplied to the burner 4 acting to reduce the combustion temperature. of the.air/.. I FOREIGN PATENTS fuelmlxwre- 1,285,210 1/1962 France.

References 1,103,687 3/1961 Germany. UNITED STATES PATENTS 256,077 7/1948 Switzerland.

2,358,815 9/1944 Lysholm 60-39.27 XR 5 2,595,505 5/1952 Bachle XR CARLTON R. CROYLE, Prlmary Examiner 2,616,252 11/1952 Robinson et a1. 6039.65 XR US. Cl. X.R. 2,633,698 4/1953 Nettel 6039.52 XR 6039.65

2,812,637 11/1957 Fox 60-3965 XR 

